I've been tasked with creating a database for a research project, mapping economic data for a number of cities around the world. I'm a database newby, and was looking for advice on the right database and interface for the job. I need it to be:

-work on as many operating systems as possible. I am on a PC (Windows 7), but there may be people on macs and linux machines wanting to have a go. It will likely be hosted on a Windows server, though.
-Be able to interface with GIS. ArcGIS would be great, but something opensource like QGIS would probably fit better with the whole public-accessible focus of the project.
-Ideally, be able to interface with the web so others can download data from it.
-Be able to do some rather complex statistical analysis, like regression, spearmans correlation, etc. I wouldn't be opposed to using another program like r, but I would like everything to be able to talk to each other, and not have to re-built relationships in different programs... The ability to summarise things graphically would be good. Perhaps it is best to export the relevant data and do the analysis elsewhere, though.
-Can grow big, but likely won't be huge. I don't think it will ever be more than 10GB
-Safe - i.e. unlikely someone will accidentally delete everything

I've had a read about mySQL and Postgresql, and have had a quick play with OpenOffice Base (which seems reasonable). I wonder if any experts have some insight.